(1)ATOLL RESEflliCH BULLETIN Notes on the Wedge-tailed Shearwater at J-Ieron Island, Great Barrier Reef, Australia A

ATOLL

RESEflliCH BULLETIN

Notes on the Wedge-tailed Shearwater at J-Ieron Island, Great Barrier Reef, Australia

A. 0 . Gross, J. M. Moulton, and C. E. Huntington

Issued by

THE 'PACIFIC SCIENCS BOARD

National Academy of Sciences--National Research Council Washington, D. C.

November 1-5, 1963

Notes on t h e Wedgetailed Shearwater a t Heron I s l a n d , Great E a r r i e r Reef, A u s t r a l i a

A . 0. ~ r o s s l , J . M. Moultonly2, and C. E. ~ u n t i n ~ t o n l ~ ~

Introduction

During t h r e e weeks of t h e southern summer, December 10, 1960 t o January 1, 1961, two of us ( ~ r o s s and ~ o u l t o n ) had an opportunity t o study t h e behavior and e a r l y n e s t i n g a c t i v i t i e s of t h e Wedge-tailed Shearwater Puffinus p a c i f i c u s

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chlororhynchus Lesson, l o c a l l y known a s t h e Mutton Bird, on Heron I s l a n d in t h e Capricorn Group a t t h e southern end of t h e Great B a r r i e r Reef, F a c i l i t i e s of t h e Heron I s l a n d Research S t a t i o n of t h e Great B a r r i e r Reef Committee a r e g r a t e f u l l y acknowledged.

Moulton was conducting a research program on Heron Island a t t h e Marine Research S t a t i o n during October and November, 1960, during which he observed t h e annual a r r i v a l of t h e b i r d s , t h e i r mating and nesting, and recorded t h e i r c a l l s . Thus t h e period of observation extended through t h r e e months of t h e b i r d ' s breeding season of 1960-1961, and i n December Gross and Moulton worked together. The topography and vege- t a t i o n of Heron I s l a n d have been described by Fosberg, Thorne, and Moulton (1961).

The Wedge-tailed Shearwater i s one of t h e most common and wide- spread shearwaters of t h e t r o p i c a l and semi-tropical p a r t s of t h e Pacific. I t s breeding range extends from t h e R e v i l l a Gigedo I s l a n d s off Baja C a l i f o r n i a t o t h e Seychelles and lviascarene I s l a n d s o f f Mada- gascar and from t h e Pescadores Islands i n Formosa S t r a i t s t o Henderson I s l a n d i n t h e southeastern Tuamotus. I t s southernmost breeding s t a t i o n s a r e o f f t h e southeast c o a s t of A u s t r a l i a and i t s northernmost in t h e Leeward Hawaiian and Bonin Archipelagoes. I t s d i s t r i b u t i o n and system- a t i c s have been discussed by Murphy (1951) who recognized two subspecies, Puffinus p a c i f i c u s p a c i f i c u s of t h e Kermadecs, F i j i s , and Norfolk Island, and

P.

2 . chlororhynchus, occupying t h e r e s t of t h e range. Oliver (1955) believes t h a t t h e s e b i r d s do not migrate, but remain in t h e s e a s adjacent t o t h e breeding i s l a n d s o u t s i d e t h e n e s t i n g season; t h e i r g r e a t powers of

Department of Biology, Bowdoin College, Brunswick, Maine.

Observations were made during tenure of a F u l b r i g h t Scholarship a t t h e University of Queensland, Department of Zoology, and of a John Simon Guggenheim Memorial Foundation Fellowship. Support was a l s o provided by National Science Foundation Grant G-44.03 and the Woods Hole Oceanographic I n s t i t u t i o n .

Supported by NSF Research Grant G5575 and NSF Undergraduate Research P a r t i c i p a t i o n Grant G11869.

f l i g h t a l l o w them t o r a n g e widely, however, a s i n d i c a t e d by Murphy's r e p ~ r t o f specimens t a k e n hundreds o f m i l e s from a n y p o s s i b l e b r e e d i n g s t a t i o n .

The Wedge-tailed S h e a r w a t e r i s known by s e v e r a l common names i n d i f f e r e n t a r e a s o f i t s d i s t r i b u t i o n , s u c h as Wedge-tailed P u f f i n , Wedge- t a i l e d P e t r e l , Mourning B i r d , Moaning B i r d , o r Ghost E i r d because o f i t s c a l l , B l a c k Burrowers and t h e u s u a l name, Mutton B i r d , The l a t t e r name i s a p p l i e d t o s e v e r a l o t h e r s p e c i e s such as P. t e n u i r o s t r i s ,

g.

g r i s e u s ,

P.

c a r n e i p e s , a n d P. b u l l e r i . The name Mutt& B i r d a r o s e from t h e

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t a s t e o f t h e flesh:

D e s c r i p t i o n

The plumage o f t h e Wedge-tailed S h e a r w a t e r shows two c o l o r phases.

The d a r k phase h a s t h e upper s u r f a c e o f t h e plumage a s o o t y brown, t h e p r i m a r i e s and t a i l a r e b l a c k , t h e c h i n , t h r o a t , and f o r e h e a d brownish g r a y , and t h e r e m a i n d e r o f t h e u n d e r s u r f a c e a dusky brown. I n t h e l i g h t phase t h e b i r d s a r e brown above, b u t t h e under p a r t s a r e w h i t e w i t h g r a y a l o n g t h e b o r d e r s between t h e two c o l o r s . The under t a i l c o v e r t s a r e b l a c k i n b o t h forms, The b i l l i s s l a t e o r l e a d c o l o r , t h e i r i s d a r k b r o w n , . t h e t a r s u s , f o o t , and n a i l s f l e s h c o l o r , and t h e o u t e r edge of t h e o u t e r t o e s d a r k l y pigmented. The o u t e r t o e s a r e s t r o n g e r , t h i c k e n e d , and c a l l o u s e d , probably due t o t h e g r e a t e r u s e o f t h e s e t o e s i n d i g g i n g .

Only t h e d a r k forms a r e f o u n d on Heron I s l a n d . The Wedge-tailed S h e a r w a t e r i s polymorphic, t h e l i g h t and d a r k p h a s e s o c c u r r i n g t o g e t h e r i n some c o l o n i e s , w h i l e a t h i r d i n t e r m e d i a t e form i s sometimes fotmd (Murphy, 1951). Although t h e p r o p o r t i o n o f l i g h t phase b i r d s i s h i g h e r in t h e n o r t h e r n p a r t of t h e r a n g e , t h e s e c o l o r p h a s e s do n o t c o n s t i t u t e g e o g r a p h i c a l s u b s p e c i e s , as was f o r m e r l y m a i n t a i n e d (Loomis, 1923), G e o g r a p h i c a l v a r i a t i o n , b o t h i n s i z e and i n c o l o r phase p r o p o r t i o n s , o c c u r s w i t h i n t h e s u b s p e c i e s

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P u f f i n u s

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p a c i f i c u s chlororhynchus. A number of a l b i n i s t i c and s e m i - a l b i n i s t i c forms of t h e Wedge-tailed S h e a r w a t e r have a l s o been r e p o r t e d (lrlunro, 1944).

Measurements in m i l l i m e t e r s a n d w e i g h t s in grams o f f i v e specimens o f Wedge-tailed S h e a r w z t e r s from Heron I s l a n d a r e g i v e n in Table I. The measurements and w e i g h t s a r e o f l i v i n g b i r d s , s e x e s n o t determined. The n o s t r i l - b i l l measurements were f r o m t h e a n t e r i o r edge o f t h e n o s t r i l opening t o t h e t i p o f t h e b i l l , The eye-bill measurement was t h e d i s - t a n c e from t h e a n t e r i o r edge o f t h e e y e t o t h e t i p o f t h e b i l l .

h he

o t h e r measurements a r e s t a n d a r d , )

Table I

Measurements in millimeters and weights in grams of f i v e a d u l t Heron I s l a n d Wedge-tailed Shearwaters

Length Extent

Wing

Tarsus Foot

~ i l l ( c u l m e n ) N o s t r i l - b i l l Eye-bill Weight

Mean

437

l O I &

294 49

54 33

3 2 53 404

Some measurements of 5 birds, 2 males and

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females, from t h e Tonga I s l a n d s were made by Davidson (1931) on January 6, 1921:

Wing T a i l Culmen Tarsus

Average 2 males 289.0 135.5

41

25 46

Average 3 females 289.0 135.0 39.0 39-0

A r r i v a l a t Heron I s l a n d

No Wedge-tailed Shearwaters were observed on Heron I s l a n d when Pioulton a r r i v e d on t h e i s l a n d f o r t h e f i r s t time on October

4,

1960, He captured and. photographed one of t h e f i r s t a r r i v a l s of 1960 near t h e Marine S t a t i o n on October 8, 1960, and t h e f i r s t c a l l notes of t h e y e a r were heard l a t e r t h a t night. By October 11 l a r g e numbers had a r r i v e d and were present from then on u n t i l our departure. Many of t h e shear- waters fed a t sea during t h e day, o f t e n with Noddy Terns, Anous sp.

None of them were seen on t h e i s l a n d during t h e day, except in burrows, but thousands of them poured onto t h e i s l a n d a t dusk and departed t h e next morning. By November inany f r e s h burrows had been excavated in t h e

sand and apparently o l d ones were renovated and lengthened.

The Nest Burrow

The openings of t h e tunnels l e a d i n g t o t h e n e s t i n g c a v i t y a r e u s u a l l y wider than high and l a r g e enough t o admit t h e b i r d s with room t o spare, Five r e p r e s e n t a t i v e openings were 1 0

x 15, 9

x

15, 13 x 13,

1 0 x 18, and 20 x 25 centimeters i n s i z e . The l e n g t h of tunnel v a r i e s with repeated use, t h e character of t h e s o i l , and o b s t r u c t i o n s encount- ered i n digging. I n some cases i n which t h e t u n n e l was l e s s than half a meter long we could see t h e egg o r t h e incubating bird; a few t u n n e l s were a s long a s

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meters. The majority of t h e n e s t s could be e a s i l y reached by i n s e r t i n g t h e arm and required no excavation t o obtain t h e a d u l t b i r d o r i t s egg. The n e s t s had only a scant l i n i n g of grasses and twigs and it was not unusual t o f i n d t h e egg on t h e sandy bottom of t h e n e s t i n g bowl without any n e s t i n g material. The excavated tunnels s t a r t e d down u s u a l l y a t a s l i g h t angle and then p a r a l l e l e d t h e s u r f a c e of t h e ground. The burrows of former y e a r s were renovated and were dug much longer than t h e f r e s h l y dug tunnels.

Several of t h e b i r d s were seen digging t h e i r n e s t i n g holes a t t h e s t a r t , i n which t h e l e g s and f e e t play an important role. The b i r d would r e s t on i t s s i d e and by extremely rapid s t r o k e s of t h e l e g would make t h e sand spray upwards f o r a s much a s a meter. P r e s e n t l y t h e b i r d would t u r n t o i t s o t h e r s i d e and continue digging with t h e opposite f o o t . The t a r s i of t h e Wedge-tailed Shearwater a r e long and strong and well adapted t o digging. The beak, contrary t o what one might expect, was not used t o any g r e a t extent i n digging. The burrows on Heron I s l a n d were very c l o s e together, sometimes

3

o r

4

t o t h e square meter, so t h a t t h e ground was almost completely undermined. I n walking a c r o s s a n e s t i n g a r e a , one was constantly breaking through i n t o t h e burrows even i n places where t h e surface of t h e ground seemed t o be f i r m and s o l i d . IYIany of t h e n e s t i n g burrows on Heron I s l a n d were under and among t n e tangled r o o t s of Pisonia and o t h e r t r e e s . I n a s e c t i o n of t h e n e s t i n g area near t h e guest houses of the h o t e l t h e birds tunneled under t h e buildings and o t h e r s t r u c t u r e s . A l a r g e water tank r e s t i n g on the ground was so completely undermined with tunnels made by t h e b i r d s t h a t it sank deeply on one s i d e and had t o be r e s e t . The custom i s t o 12y chicken wire (wire n e t t i n g ) around buildings t o prevent burrowS ng underneath.

The cabin which t h e senior author occupied bias i n t h e midst of a heavily populated section of t h e shearwater colony. An a r e a of 20 x 25 meters had been cleared of vegetation and l e v e l e d d i r e c t l y i n f r o n t of our cabin. Approximately 50 p i r s of b i r d s continued t o use the a r e a i n s p i t e of t h e r a d i c a l changes made by man's i n t r u s i o n . Banding of b i r d s elsewhere has revealed t h a t o t h e r shearwaters and p e t r e l s p e r s i s t i n occupying t h e t r a d i t i o n a l grounds, even r e t u r n i n g t o t h e same

burrow i f it remains i n t a c t from one n e s t i n g season t o the next.

The Egg

The onset of egg-laying occurred with s u r p r i s i n g uniformity.

Although more than twenty burrows i n d i f f e r e n t s e c t i o n s of t h e i s l a n d

were examined a l m o s t d a i l y , t h e f i r s t eggs were n o t found u n t i l 1 5 December. On t h a t d a t e we suddenly found eggs commonly, t h e major- i t y o f n e s t s examined c o n t a i n e d an egg where b e f o r e t h e r e had b e e n none, and s e v e r a l eggs were found f r e s h l y l a i d on t h e s u r f a c e of t h e ground.

The o c c u r r e n c e of a l a r g e number of eggs on t h e open ground i s d i f f i c u l t t o e x p l a i n , b u t i t i s p o s s i b l e d e p o s i t i o n on t h e ground o c c u r r e d when a burrow had n o t y e t been e x c a v a t e d o r when a burrow had been f i l l e d i n .

A n e s t i n g a r e a n e a r t h e h o t e l b u i l d i n g s was v e r y much dug up by t h e b i r d s . The a r e a was smoothed o v e r by a t r a c t o r s c r a p e r , f i l l - i n g up a l l o f t h e n e s t i n g t u n n e l s . It was a t t h e b e g i n n i n g of t h e e g g - l a y i n g s e a s o n , and a s a r e s u l t t h e b i r d s seemed b e w i l d e r e d when t h e y appeared i n t h e evening. Many eggs were d e p o s i t e d on t h e ground d u r i n g t h e n i g h t , b u t s u c h eggs were n e v e r i n c u b a t e d , a l t h o u g h ac- c o r d i n g t o :lowell and Bartholomew (1961) on Midway I s l a n d lithe Wedge-tailed S h e a r w a t e r commonly n e s t i n s h a l l o w d e p r e s s i o n s o f t h e sand. The n e s t i s u s u a l l y i n a t l e a s t p a r t i a l s h a d e , b u t i n r a r e i n s t a n c e s n e s t s were p l a c e d c o m p l e t e l y i n t h e open.': I n 1910 on Raoul I s l a n d o f t h e Kermadec group many eggs o f t h e IJedge-tailed Shearwater were l a i d on t h e s u r f a c e o f t h e ground; i n t h e p r e v i o u s y e a r a s t o r m f i l l e d many o f t h e burrows w i t h sand and r o c k s , which s e t s o h a r d t h e bFrds c o u l d n o t burrow ( O l i v e r , 1955).

The s i n g l e egg of t h e V e d g e - t a i l e d S h e a r w a t e r i s e l o n g a t e , o v a t e i n shape and pure w h i t e i n c o l o r w i t h a m a t t e s u r f a c e . Ten eggs measured by us v a r i e d i n l e n g t h from 60.3 t o 68.2 mm. (mean 6 2 . 7 ) , i n w i d t h from 40.7 t o 43.0 mm. (mean 41.8), and i n weight from 53.7 t o 6 4 . 1 grams (mean 59.0). These means a r e c l o s e t o t h o s e g i v e n by Bent (1922). O t h e r d a t a have been p u b l i s h e d by O l i v e r (1955) and W i l l e t t (1919) f o r o t h e r i s l a n d s .

When b o i l e d , t h e egg was f u l l y a s p a l a t z b l e a s a h e n ' s egg and d i d n o t have t h e f i s h y odor o r t a s t e t h a t a r e a s s o c i a t e d w i t h t h e eggs of many o t h e r s e a b i r d s . The y o l k was a p a l e yellow. The w h i t e o f t h e Mutton B i r d ' s egg i s l i k e t h a t of t h e h e n ' s egg. It i s n o t s u r - p r i s i n g t h a t t h e Maoris of New Zealand p r i z e t h e eggs a s w e l l a s t h e

f l e s h of o t h e r s h e a r w a t e r s as food.

Sex D e t e r m i n a t i o n

S i n c e t h e s h e a r w a t e r s e x h i b i t no e x t e r n a l s e x u a l dimorphism we used t h e method used by S e i v e n t y (1956a) i n s e x i n g p e t r e l s and s h e a r - : , ~ a t e r s by an e x a m i n a t i o n of t h e c l o a c a . T h i s method i s a p p l i c a b l e d u r i n g t h e p e r i o d o f s e x u a l a c t i v i t y . The d i f f e r e n c e between t h e s e x e s l i e s i n t h e g r e a t d i l a t i o n o f t h e c l o a c a a s s o c i a t e d w i t h t h e s w e l l i n g o f t h e o v i d u c t of t h e f e m a l e , t o a l l o w f o r t h e p a s s a g e o f t h e Large egg. We examined a s e r i e s o f b i r d s and found t h e method e a s y and a p p a r e n t l y a c c u r a t e . To check t h e s e x i n g , a n i n c u b a t i n g b i r d determined t o be a male by t h e c l o a c a 1 e x a m i n a t i o n was c o l l e c t e d ; d i s s e c t i o n proved t h e d i a g n o s i s t o be c o r r e c t . F?e examined s i x b i r d s

from n e s t s soon a f t e r t h e egg was deposited; a l l six were males.

This was evidence t h a t t h e male t a k e s p a r t i n incubation and probably i n i t i a t e s it. Three males were banded which were incubating eggs, and in one case a female replaced the,male a f t e r s i x days. Unfortun- a t e l y , t h e other two n e s t s were a c c i d e n t a l l y destroyed. It i s c e r t a i n t h a t both male and female normally take p a r t i n incubation. The male may be t h e one of t h e p a i r t o excavate t h e burrow, but no s e x deter- mination was made of t h e few b i r d s seen digging burrows. More obser- vations a r e needed t o determine the time spent on t h e n e s t by each s e x and t h e number of times changes a r e made during t h e e n t i r e period of incubation.

The door and a window of our cabin faced t h e cleared area, giving us an unexcelled opportunity t o observe, by means of f l a s h l i g h t s and e l e c t r i c l i g h t s , t h e a c t i v i t i e s of t h e b i r d s a t a l l hours of t h e night.

Here we could repeatedly record t h e time of t h e i r a r r i v a l and departure and note t h e d e t a i l s of t h e i r behavior.

During t h e day t h e shearwaters were not i n evidence on t h e i s l a n d ; a l l but those incubating i n t h e i r burrows were s c a t t e r e d , feeding o u t a t sea. Some were seen by various observers more than a hundred miles from t h e colony, They seem t o be widely dispersed i n small groups but have been seen concentrated i n very l a r g e numbers, sometimes with Noddy Terns, i n places where food has abundant. The Wedge-tailed Shearwaters do not feed on f i s h t o any g r e a t extent. The food, judging from stomach examinations, i s c h i e f l y cephalopods such a s squids, shrimps, and o t h e r small crustaceans which a r e caught near the surface of t h e water. F a r out a t sea s i n g l e i n d i v i d u a l s o r small groups of 2 t o

5

may be seen seeking food and occasionally s i t t i n g on t h e water. The shearwaters a r e expert f l i e r s and with t h e i r long narrow wings maneuver e x p e r t l y a s they skim c l o s e l y over t h e waves with l i t t l e movement of t h e i r wings;

t h e i r f l i g h t resembles t h a t of t h e a l b a t r o s s e s , but with more flapping.

On a t y p i c a l evening in December t h e Noddy Terns were t h e f i r s t t o return; a few of them would be seen going t o o r from t h e i s l a n d a t any hour of t h e day, but by h:30 p.m. t h e vanguard of t h e g r e a t masses of t e r n s coming t o t h e Heron I s l a n d rookery f o r t h e n i g h t had arrived.

Some of t h e b i r d s came in a s s i n g l e i n d i v i d u a l s , but most of them were in groups of t e n o r more. By 7:00 p.m, t h e t e r n s were a r r i v i n g by t h e thousands a l l along t h e e a s t e r n s i d e of t h e i s l a n d

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a s many a s 350 per minute within 30 meters of t h e beach.

A t

7:45

p.m. t h e l i g h t was growing dim and suddenly t h e r e was an awe-inspiring r o a r of wings: t h e shearwaters had a r r i v e d o f f shore.

Thousands of them were c i r c l i n g and f l y i n g about before venturing inland. A few minutes l a t e r they would f l y over l i k e a swarm of huge bats. They continued t o f l y back and f o r t h over t h e e n t i r e n e s t i n g a r e a of t h e island.

A t t h e c l e a r i n g near t h e camp a few minutes a f t e r 8:00 p.m. a dozen o r more shearwaters c i r c l e d high above t h e t r e e tops. It was too dark t o see t h e d e t a i l s of t h e n e s t i n g a r e a without l i g h t s , but t h e b i r d s were d a r k l y s i l h o u e t t e d a g a i n s t t h e s t a r l i t s b above. The b i r d s u t t e r e d no c a l l s . A s they c i r c l e d and came nearer and n e a r e r t o t h e ground they seemed t o be searching f o r a proper place t o land near t h e i r burrows. Around 8:30 p.m. t h e f i r s t b i r d would l i t e r a l l y drop t o t h e ground with a d i s t i n c t thump in a resounding pancake

landing, withdrawing t h e f e e t and f o l d i n g t h e wings a t about l$ meters above ground. It d i d not land on i t s f e e t nor d i d i t break i t s down- ward speed by using i t s t a i l and wings e f f e c t i v e l y . (Odd b i r d s crashed i n t o l i g h t e d windows.) The b i r d s were not stunned but, l i n g e r i n g long enough t o g e t t h e i r bearings, they scooted towards t h e entrance of a burrow where they might be met by t h e i r mates. A t t h e proper burrow t h e two b i r d s seemed t o exchangs subdued c a l l s of recognition. One newly-arrived b i r d appeared t o be feeding i t s mate by r e g u r g i t a t i o n , but we were unable t o observe t h e t r a n s f e r of t h e food. The t w o b i r d s came c l o s e t o g e t h e r and one of them repeatedly r a n i t s beak through t h e f e a t h e r s of t h e neck and head of i t s mate. This behavior may have been a p a r t of t h e c o u r t s h i p performance. A t such times a pungent o i l was emitted from t h e n o s t r i l s a s occurs i n o t h e r p e t r e l s . Soon o t h e r b i r d s made s i m i l a r landings i n quick succession, and t h e majority of them

joined t h e i r mates, not i n t h e burrows as might be expected but on t h e open ground where they remained f o r t h e night. Courtship including copulation usually took place not in t h e burrows but on open ground.

The b i r d s do not stand upright on t h e i r f e e t but r e s t t h e i r bodies f l a t on t h e sand. A b i r d e n t e r i n g a wrong burrow was vigorousxy ousted by t h e t e n a n t which obviously was n o t i t s mate. This o u s t i n g was

accompanied by loud yowls and v i o l e n t flappings of wings. A t t h i s time t h e c a l l s and weird sounds of t h e b i r d s made t h e n i g h t hideous and ghostly. They came from thousands of b i r d s i n every p a r t of t h e nest- i n g a r e a of t h e whole i s l a n d , The c a l l s were not b i r d - l i k e and n o t musical but were high-pitched c a t - l i k e s q u a l l s mingled with low-

- pitched murmurs. A t times t h e i r c a l l s resembled those of cows and t h e i r calves, and again i t was l i k e a l i v e l y and s p i r i t e d c a t serenade.

The s i l e n c e of day was rudely broken, a s darkness descended, by t h e i r weird dolorous wails.

The chorus of thousands of shearwaters mingled with t h e high- pitched c a l l s of t h e noddy t e r n s i n t h e i r wooded rookery was kept up throughout t h e n i g h t without any marked intermission. The b i r d s were s t i l l going s t r o n g a t

5:OO

a.m., but soon t h e r e a f t e r t h e volume of sounds began t a p e r i n g o f f . There was much a c t i v i t y among t h e shear- waters, t h e b i r d s running r a p i d l y and awkwardly, scooting over t h e ground with t h e i r wings upheld t o balance themselves. Evidently with t h e i r heavy bodies and wing spread of a meter it was d i f f i c u l t t o t a k e off i n a r e s t r i c t e d area. I n s t e a d t h e r e would be a stampede of b i r d s rushing along t h e ground t o t h e shore along well-defined paths. Some of t h e b i r d s i n t h e i r confusion banged a g a i n s t our camp with such f o r c e t h a t it was s u r p r i s i n g t h a t no dead o r stunned b i r d s were found on Heron Island. The exodus was r a p i d and by 5:30 a.m. no b i r d s were seen on t h e breeding grounds. The thousands of shearwaters were o f f f o r another day on t h e i r hunting grounds a t sea.

C a l l s

We were p a r t i c u l a r l y i n t e r e s t e d i n t h e Mutton Bird because of t h e e x t e n t t o which i t s breeding and n e s t i n g behavior p a r a l l e l t h a t of Leach's P e t r e l , Oceanodroma leucorhoa ( ~ i e i l l o t ) , which has been studied f o r many years a t t h e Bowdoin S c i e n t i f i c S t a t i o n a t Kent I s l a n d i n Canadals Bay of Fundy (w.A.o. Gross, 1935; G r i f f i n , 1940;

A -0. Gross, 1947; Huntington, 1962.) Actually, although members of t h e same o r d e r ( ~ r o c e l l a r i i f o m e s )

,

t h e two b i r d s a r e i n d i f f e r e n t f a m i l i e s ( ~ r o c e l l a r i i d a e

-

Shearwaters and Fulmars, and Hydrobatidae- Storm p e t r e l s ) which share many c h a r a c t e r i s t i c s , including n e s t i n g underground on o f f s h o r e i s l a n d s , l a y i n g a s i n g l e egg, going and coming by n i g h t , feeding a t sea, c a l l i n g on t h e breeding grounds, t h e sexes being a l i k e e x t e r n a l l y , and e j e c t i n g a stomach o i l of c h a r a c t e r i s t i c odor a

The c a l l s of Leach's P e t r e l have been recorded by Huntington, P h i l i p D. Walls, Lowry C. Stephenson, and D. ~ a r r y May. This p e t r e l makes a " f l i g h t c a l l N heard a t - n i g h t over t h e nesting grounds and occasionally a t sea, and a "burrow c a l l I t o r "purring c a l l n produced i n the burrow. The purring c a l l may be r a r e l y produced on t h e wing, and the f l i g h t c a l l i s commonly produced i n t h e burrow. While t h e f l i g h t c a l l i s produced somewhat i r r e g u l a r l y , t h e purring c a l l i s produced over and over again by an undisturbed bird. When it i s heard from a burrow, usually two b i r d s a r e present, and t h e c a l l i s o f t e n heard a s a duet (palmer, 1962, p. 228). The f l i g h t c a l l con- s i s t s of two d i s t i n c t i v e s t a c c a t o phrases, separated by a brief pause

able

11); it v a r i e s g r e a t l y i n p i t c h and p a t t e r n d e t a i l s .

The Mutton Bird, on t h e o t h e r hand,produces a moan-like c a l l which v a r i e s in p i t c h from one i n d i v i d u a l t o another, but i s too simple t o a.llow v a r i a t i o n i n p a t t e r n . It i s made by birds l y i n g on t h e ground and by b i r d s i n t h e burrow. It may sound l i k e a c a t e r - wauling, a howl, a low moan, and during f i g h t i n g l i k e a s n a r l . The b i r d s a r e q u i e t whenever they e n t e r a l i g h t e d area, and we never heard them c a l l i n g a t sea o r on t h e wing.

Recordings were made of Heron I s l a n d Mutton Birds i n t h e v i c i n i t y of t h e laboratory building of t h e Great B a r r i e r Reef Committee on

October

14,

1960, with a Magnecorder PT~-BN and a PT~BAWZ tape recorder and an Electro-Voice 630 microphone around 10:OO p.m. a t

3

3/4 inches/

second. Recordings of Leach's P e t r e l s were made on Kent Island, Grand Manan, on May 25, 1962, around 10:45 p.m. with a Magnemite Recorder

610-EV, and Electro-Voice 630 microphone and a 30-inch parabolic r e f l e c t o r a t 15 inches/second; o t h e r recordings were made on G u l l I s l a n d , 20 miles south of S t . John's Newfoundland, a t

1:45

a.m. on August

14,

1962. Sound spectrograms were prepared on a Kay Vibralyzer

v i b r a t i o n frequency analyzer,and time-frequency d a t a a r e taken from those preparations, C h a r a c t e r i s t i c s of Mutton Bird and Leach's P e t r e l c a l l s a r e shown in Table 11.

C a l l

.-

Mutton

B i r d

Leach's P e t r e l

F l i g h t c a l l

Leach's P e t r e l

Burrow c a l l

---- ^Duration

- -

1-29 seconds ( ~ a n g e 1.13 - ^1.47)

Mean of 5 c a l l s

1.02 seconds (Range , 8 -

^{1 . 2 )}

Mean of 5 calls

2.5 seconds between clucks

(1

c a l l

measured)

Frequency Span I General d e s c r i p t i o n

88 t o over 8800 cps with most sound energy between 615 and 4100 cps

- -- -- - -

Measurements of fundamental:- Mean of 5 s t a r t s 279 cps

(225 - ³¹⁵⁾

of 5 peaks 419 cps

A

s e r i e s of 10 o r

11

r a p i d l y e m i t t e d notes, u s u a l l y i n t h e follow- i n g pattern:.

- -- --

C a l l

v a r i e s from a low moan t o a h a r s h s n a t l

Purring:. up t o 6500 cps with most sound energy below 2200 cps i n a har- monic p a t t e r n . Ascending

sound: 250-570 cps. Cluck:

88 t o over 8800 cps i n a harmonic p a t t e r n

(270 - ⁵⁰⁰⁾

Mean of 5 ends 297 cps

(180 - ³⁶⁰⁾ I

There a r e u s u a l l y

2

harmonics ,

A

prolonged purring

i n t e r r u p t e d periodi-

c a l l y ( a f t e r 56 n o t e s

i n one c a s e ) by the

ascending sound o f

indrawn b r e a t h sad a

s h a r p d u c k

The nesting season of t h e Wedge-tailed Shearwater v a r i e s in t h e d i f f e r e n t p a r t s of i t s extensive l a t i t u d i n a l range. I n t h e northern colonies t h e time i s i n t h e northern spring, while i n t h e southern P a c i f i c it i s i n t h e southern spring ( ~ u r ~ h y , 1951).

A t Heron I s l a n d t h e f i r s t b i r d ms seen on October 8 t h and t h e f i r s t egg on December 15th. Egg-laying was a t i t s height a t t h e end of December. The incubation period of t h e Wedge-tailed Shearwater i s

somewhat l e s s than two months, while fledging r e q u i r e s a t l e a s t t h r e e months, according t o O l i v e r (1955).

We a r e indebted t o M r . H. ^{F s} Manning f o r information concerning t h e s t a t u s of t h e shearwaters on Heron I s l a n d a f t e r our departure. A few of t h e a d u l t b i r d s l e f t i n March, 1961, but most of t h e a d u l t s do not u s u a l l y leave u n t i l May. The b i r d s a r e extremely noisy before t h e i r departure, and on t h e following day a l l i s deathly q u i e t . The young a r e deserted i n t h e i r burrows, where they remain u n t i l they a r e

a b l e t o s h i f t f o r themselves.

The Short-tailed Shearwater does not acquire sexual maturity u n t i l s i x o r more years of age (Serventy, l956b). As a s i m i l a r period may e x i s t f o r t h e Wedge-tailed Shearwater, a l a r g e portion of t h e b i r d s present on Heron I s l a n d may be non-breeding individuals.

Summary

Wedge-tailed Shearwaters n e s t i n g a t Heron Island were observed from t h e i r a r r i v a l on October 8, 1960, u n t i l January 1, 1961. Measure- ments of f i v e unsexed l i v i n g specimens and t e n eggs were obtained.

Widespread egg-laying began a b r u p t l y on December 15th. Hany eggs were l a i d on t h e ground, but were n o t incubated. Nest-building, n i g h t l y a r r i v a l s and departures, courtship, copulation, and c a l l s were observed and described. Sowd spectrograms of t h e c a l l s were compared with

those of another tube-nose, Leach's P e t r e l , and found t o be much simpler and l e s s variable.

L i t e r a t u r e Cited

Bent, A . C. 1922. L i f e h i s t o r i e s of North American p e t r e l s and p e l i c a n s and t h e i r a l l i e s .

Bull. U, S. Nat. Mus. 121:

1-343.

Davidson, M. E. M. 1931. On t h e breeding of Puffinus chlororhsmchus i n t h e Tonga group.

Condor 33: 217-218.

Fosberg, F. R., R. F. Thorne, and J. Me Moulton 1961. Heron I s l a n d , Capricorn Group, A u s t r a l i a ,

A t o l l Research B u l l e t i n 82:

1-16,

G r i f f i n , D. R. 194.0, Homing experiments with Leach's p e t r e l , The Auk

57:

61-74

Gross, A. 0. 1947. Recoveries of banded Leach's p e t r e l s . Bird-Banding 18 : 117-126.

Gross, W. A. 0. 1935. The l i f e h i s t o r y c y c l e of Leachrs p e t r e l (~ceanodroma leucorhoa leucorhoa) on t h e o u t e r i s l a n d s of t h e Bay of Fundy.

The Auk 52: 382-399

Howell, T. R., and G. A. Bartholomew 1961. Temperature r e g u l a t i o n in n e s t i n g Bonin I s l a n d p e t r e l s , wedge-tailed shearwaters and Christmas I s l a n d shearwaters.

The A&

78:

343-354.

Huntington, C . E, 1962. The population dynamics of Leachr s p e t r e l , Oceanodroma leucorhoa,

Abstracts of Papers, X I I I t h I n t . Ornith. Cong.

Loomis, L. M. 1923. The c l a s s i f i c a t i o n of t h e a l b a t r o s s e s , p e t r e l s and diving p e t r e l s .

The Auk 40: 596-602.

Munro, G. C , 1944. B i r d s of Hawaii,

Tongg Publishing Company, Honolulu, Hawaii.

Mur);hy, R. C 1951. The populations of t h e wedge-tailed shearwater ( ~ u f f inus pacif i c u s )

.

American Museum Novitates 1512: 1-21.

Oliver, W. R. B. 1955* New Zealand Birds.

A. H. and A. W. Reed, Wellington, New Zealand.

Palmer, R. S., Ed. 1962. Handbook of North American Birds, Vol. I.

Yale Univ. Press, New Haven, Connecticut. 567 pp.

Serventy, D. L. 1956a. ^A method of sexing p e t r e l s in f i e l d observations.

Emu 56: 313-3Ue

---

1956b. Age a t f i r s t breeding of t h e short-tailed shear- water, Puffinus t e n u i r o s t r i s ,

I b i s 98: 532-533.

W i l l e t t , Go 1919. Notes on t h e n e s t i n g of two little-known s p e c i e s of p e t r e l ,

Condor 21: 60-61.

Captions of Photos

Upper l e f t - A c h a r a c t e r i s t i c pose of t h e Wedge-tailed Shearwater with its body r e s t i n g f l a t on t h e ground. The crossed wing t i p s extend t o near t h e end of t h e t a i l .

Upper r i g h t - - The Fledge- t a i l e d Shearwater a t l e f t approaching i t s mate, which has j u s t emerged from t h e n e s t i n g burrow,

Lower Left- The shearwater a t t h e l e f t has approached i t s mate which has come o u t of t h e n e s t i n g burrow. The b i r d s a r e b i l l i n g each o t h e r and running t h e i r beaks through t h e f e a t h e r s o f t h e neck, a p a r t of t h e c o u r t s h i p performance.

Lover r i g h t - - Three eggs of t h e Fledge-tailed Shearwater (Numbers 1-3 of Table 11) with a n A u s t r a l i a n sixpence, showing t h e r e l a t i v e s i z e of the l a r g e eggs.